Display device with touch panel having x, y and dummy electrodes

ABSTRACT

A display device includes a display panel, and an electrostatic capacitive type touch panel which is formed in an overlapping manner with the display panel. A plurality of X electrodes and a plurality of Y electrodes intersecting with the X electrodes. A first signal line supplies signals to the X electrodes, a second signal line supplies signals to the Y electrodes, and the first signal line and the second signal line are formed on a flexible printed circuit board. A dummy electrode is formed adjacent to an electrode portion of each X electrode and electrode portion of each Y electrode, the dummy electrode does not overlap the X electrode and the Y electrode, and the dummy electrode does not electrically connect with the first and second signal lines.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. application Ser.No. 12/534,921, filed Aug. 4, 2009, the contents of which areincorporated herein by reference.

The present application claims priority from Japanese applicationJP2008-202870 filed on Aug. 6, 2008, the content of which is herebyincorporated by reference into this application.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a display device with a touch panel,and more particularly to a technique which is effectively applicable toa display device with a touch panel which includes an electrostaticcapacitive type touch panel.

2. Description of the Related Art

Recently, a touch panel technique which assists a “user-friendly”graphical user interface has become important in the propagation ofmobile equipment.

For example, as a touch panel technique, JP-T-2003-511799 (patentdocument 1) discloses an electrostatic capacitive type touch panel. Withrespect to such an electrostatic capacitive type touch panel, there hasbeen known the touch panel which can detect a touch position touched bya viewer.

The touch panel described in patent document 1, however, detectscoordinates of a position touched by the viewer by detecting coupledcapacitance formed of capacitance of an electrode line in the Xdirection and capacitance of an electrode line in the Y direction.

SUMMARY OF THE INVENTION

An electrostatic capacitive type touch panel includes a plurality of Xelectrodes which extends in the first direction (for example, Ydirection) and is arranged parallel to each other in the seconddirection (for example, X direction) which intersects with the firstdirection, and a plurality of Y electrodes which extends in the seconddirection while intersecting with the X electrodes and is arrangedparallel to each other in the first direction. Such a touch panel isreferred to as an X-Y type touch panel.

In the X-Y type touch panel, the plurality of X electrodes and theplurality of Y electrodes are stacked on a substrate with an interlayerinsulation film sandwiched therebetween. These X electrodes and Yelectrodes are formed using a transparent conductive material such asITO (Indium Tin Oxide) or the like, for example.

In the X-Y type touch panel of the related art, the capacitance ofelectrodes on one line in a state that the one-line electrode line isnot touched by a finger or the like (in a steady state) is formed ofinter-electrode capacitance between the one-line electrode and anelectrode arranged adjacent to the one-line electrode, intersectingportion capacitance which is generated at an intersecting portion whereelectrodes orthogonally intersect with each other, capacitance to groundbetween the one-line electrode and a display device arranged below thetouch panel, and line capacitance which is generated in a line between acontrol IC and the touch panel.

The electrostatic capacitive type touch panel adopts a detection methodin which the touch panel detects a capacitance change which occurs whena finger of a person or the like touches the touch panel and hence, itis desirable that the capacitances other than the inter-electrodecapacitance are as small as possible. When the inter-electrodecapacitance is larger compared to other capacitances, a sufficientcapacitance ratio can be ensured when a person touches the touch panelwith his/her finger and hence, the performance of the touch panel isenhanced. To the contrary, when the sufficient capacitance ratio cannotbe ensured, the touch panel cannot recognize that the finger or the liketouches the touch panel and hence, there may be a possibility that thetouch panel erroneously operates.

As an index of detection sensitivity of the touch panel, a ratio betweena capacitance change which occurs when a finger or the like touches thetouch panel and background noises (hereinafter indicated as an “S/Nratio”) is used. To increase the detection sensitivity, that is, S/Nratio, it is necessary to elevate a signal level or to reduce noises.

As described previously, the signal level is proportional to capacitanceformed between a finger or the like which touches the touch panel andthe electrode. On the other hand, when the line capacitance or the likeis increased, the capacitance change which occurs when the finger or thelike touches the touch panel becomes relatively small thus worsening theS/N ratio. Further, with respect to the background noises, it is foundthat the fluctuation of a signal voltage which is generated when adisplay device performs a display is detected as noises by the electrodeof the touch panel positioned directly above the display device. Thelarger a sum of electrode areas of electrodes on one line, the largerthe capacitance to ground becomes and hence, noises can be easilydetected.

Further, as a method of supplying a signal for enhancing an S/N ratio,an attempt has been made to connect both ends of each X electrode andeach Y electrode of a touch panel to lines respectively. From thisattempt, it is found that when a signal transmitted from a control IC issupplied to the X electrodes and Y electrodes through both ends of theelectrodes, an S/N ratio is enhanced.

However, since the signal is supplied from both ends of the electrode,lines connected between the control IC and the touch panel extendlaterally so that these lines intersect with other lines thus givingrise to a new drawback that line capacitance is increased.

The present invention has been made to overcome the above-mentioneddrawbacks of the related art, and it is an object of the presentinvention to provide a display device having a highly reliableelectrostatic capacitive type touch panel which allows finger touchinputting and possesses excellent detection sensitivity.

The above-mentioned and other objects and novel features of the presentinvention will become apparent from the description of thisspecification and attached drawings.

To briefly explain the summary of typical inventions among theinventions disclosed in this specification, they are as follows.

When a signal is supplied from both ends of each electrode of anX-Y-type touch panel for enhancing an S/N ratio, there arises a drawbackthat lines intersect with each other on a flexible printed circuit boardand hence, line capacitance is increased at an intersecting portion. Toovercome this drawback, the present invention adopts the structure inwhich a line including a ground potential portion is not arranged on aback surface of a portion of a line which connects an output portion ofa control IC with an electrode on a touch panel. Further, at a portionof the flexible printed circuit board where the intersection of lines isnecessary, an intersecting area is minimized by allowing the lines tointersect with each other orthogonally thus preventing the increase ofthe line capacitance.

Further, to set the capacitance of electrodes on one line equal betweenthe X direction and the Y direction, an area of respective electrodes onthe line where the number of electrodes is large is made small thussetting noise intensity equal between the X direction and the Ydirection. That is, an S/N ratio is set equal between the X directionand the Y direction.

Further, to reduce noises from a display panel, a transparent conductivefilm is formed between the display panel and the touch panel.

To briefly explain the advantageous effects acquired by typicalinventions among the inventions disclosed in this specification, theyare as follows.

According to the present invention, it is possible to provide a displaydevice having a highly reliable electrostatic capacitive type touchpanel which allows finger touch inputting and possesses excellentdetection sensitivity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view of a display device according to anembodiment of the present invention;

FIG. 2 is a schematic cross-sectional view of the display deviceaccording to the embodiment of the present invention;

FIG. 3 is a schematic plan view of a touch panel according to theembodiment of the present invention;

FIG. 4 is a schematic plan view showing a state in which a flexibleprinted circuit board is mounted on the touch panel according to theembodiment of the present invention;

FIG. 5 is a schematic cross-sectional view of the touch panel accordingto the embodiment of the present invention;

FIG. 6A and FIG. 6B are schematic cross-sectional views showing a firststep for forming the touch panel according to the embodiment of thepresent invention;

FIG. 7A and FIG. 7B are schematic cross-sectional views showing a secondstep for forming the touch panel according to the embodiment of thepresent invention;

FIG. 8A and FIG. 8B are schematic cross-sectional views showing a thirdstep for forming the touch panel according to the embodiment of thepresent invention; and

FIG. 9A and FIG. 9B are schematic cross-sectional views showing a fourthstep for forming the touch panel according to the embodiment of thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, an embodiment of the present invention is explained indetail in conjunction with drawings.

Here, in all drawings for explaining the embodiment, parts havingidentical functions are given same symbols, and their repeatedexplanation is omitted.

In this embodiment, the explanation is made with respect to a case inwhich a liquid crystal display panel is used as one example of a displaypanel. Here, the present invention is applicable to any display panelwhich can mount a touch panel thereon. Further, the display panel is notlimited to the liquid crystal display panel, and the display panel maybe a display panel which uses organic light emitting diode elements(OLED) or surface conductive electron emission elements (FED).

FIG. 1 is a plan view showing the schematic constitution of a displaydevice having a touch panel according to the embodiment of the presentinvention. FIG. 2 is a cross-sectional view taken along a line A-A′ InFIG. 1.

The display device 300 of this embodiment includes, as shown in FIG. 1and FIG. 2, a liquid crystal display panel 600, an electrostaticcapacitive type touch panel 400 which is arranged on a viewer's-sidesurface of the liquid crystal display panel 600, and a backlight 700which is arranged under a surface of the liquid crystal display panel600 on a side opposite to the viewer's side. As the liquid crystaldisplay panel 600, an IPS type liquid crystal display panel, a TN typeliquid crystal display panel, a VA type liquid crystal display panel orthe like may be used, for example.

The liquid crystal display panel 600 is configured such that twosubstrates 620, 630 which are arranged to face each other in an opposedmanner are adhered with each other, and a polarizer 601 is formed on anouter surface of one substrate, and a polarizer 602 is formed on anouter surface of the other substrate. Further, the liquid crystaldisplay panel 600 and the touch panel 400 are adhered to each otherusing a first adhesive agent 501 formed of a resin, an adhesive film orthe like. Further, a front surface protective plate (also referred to asa front window) 12 made of an acrylic resin is adhered to an outersurface of the touch panel 400 using a second adhesive agent 502 formedof a resin, an adhesive film or the like.

A transparent conductive layer 603 is interposed between the liquidcrystal display panel 600 and the polarizer 601. The transparentconductive layer 603 is provided for blocking signals generated from theliquid crystal display panel 600. A large number of electrodes areformed on the liquid crystal display panel 600, and voltages are appliedto the electrodes as signals at various timings.

When the voltage of the liquid crystal display panel 600 changes withrespect to the electrodes formed on the electrostatic capacitive typetouch panel 400, such a change causes noises. Accordingly, it isnecessary to electrically shield the liquid crystal display panel 600from the noises and hence, the transparent conductive layer 603 isprovided. To allow the transparent conductive layer 603 to function as ashield, a constant voltage is applied to the transparent conductivelayer 603 from a flexible printed circuit board 71 or the like and, forexample, the voltage applied to the transparent conductive layer 603 isset to a ground potential.

Here, to prevent the influence of the noises, it is desirable to set asheet resistance value of the transparent conductive layer 603 to 150 to200Ω/□ which is substantially equal to a sheet resistance value ofelectrodes formed on the touch panel 400. It is known that a resistancevalue of the transparent conductive layer 603 is relevant to a size ofthe grain particles. By setting a heat treatment temperature at the timeof forming the transparent conductive layer 603 at 200° C. or above, thecrystallization of the transparent conductive layer 603 is enhanced sothat a sheet resistance value of the transparent conductive layer 603can be set to 150 to 200 f/J.

The resistance value of the transparent conductive layer 603 may befurther lowered. For example, by setting a heat treatment temperature atthe time of forming the transparent conductive layer 603 at 450° C., thetransparent conductive layer 603 is sufficiently crystallized so that asheet resistance value of the transparent conductive layer 603 can beset to 30 to 40 Ω/□. When the transparent conductive layer 603 forshielding the liquid crystal display panel 600 has a resistance valuesubstantially equal to or below a resistance value of the electrodesformed on the touch panel 400, the advantageous effect of suppressingthe noise can be enhanced.

A drive circuit 50 is mounted on one side of the liquid crystal displaypanel 600, and various kinds of signals are supplied to the liquidcrystal display panel 600 from the drive circuit 50. A flexible printedcircuit board 72 is electrically connected to the drive circuit 50 forsupplying signals from the outside. Further, the flexible printedcircuit board 71 is connected to the touch panel 400. A touch panelcontrol circuit (not shown in the drawing) is connected to the flexibleprinted circuit board 71, and the detection of an input position or thelike is controlled by the touch panel control circuit.

The hybrid structure in which the touch panel 400 and the front window12 are combined with the liquid crystal display panel 600 has a drawbackthat the substrate 620 of the liquid crystal display panel 600 suffersfrom low glass strength.

The substrate 620 is also referred to as a TFT substrate. Pixelelectrodes, thin film transistors and the like are formed on thesubstrate 620, and the drive circuit 50 for supplying signals is alsomounted on the substrate 620. A region of the substrate 620 on which thedrive circuit 50 is mounted projects horizontally from one edge ofanother substrate 630, and a projecting portion is integrally formedwith the substrate 620 so that the substrate 620 has a single plateshape. There exists a possibility that the substrate 620 is broken insuch a region where the drive circuit 50 is mounted. To prevent suchbreaking of the substrate 620, a spacer 30 is inserted between thesubstrate 620 and the touch panel 400 thus enhancing the strength of thesubstrate 620.

Next, FIG. 3 is a schematic view of the touch panel 400. In thisembodiment, the touch panel 400 is used in a longitudinally elongatedmanner. Here, a profile of the touch panel which is used in anoverlapping manner with the display panel has the substantially sameshape as the display panel. The display panel has a rectangular shape ingeneral, and either one of an X-directional side of the display paneland a Y-directional side of the display panel is generally longer thanthe other side. In FIG. 3, the liquid crystal display panel 600 which isused in an overlapping manner with the touch panel 400 also has alongitudinally elongated shape.

The touch panel 400 includes a glass substrate 5 which constitutes atransparent substrate. On one surface of the glass substrate 5, touchpanel electrodes 1, 2, connection terminals 7, and peripheral lines 6which connect the touch panel electrodes 1, 2 and the connectionterminals 7 are arranged. At least intersecting portions of two kinds ofelectrodes which are arranged to orthogonally intersect with each otherare separated from each other by an insulation film.

The touch panel electrodes 1, 2 are formed of a transparent conductivefilm. The electrodes which extend in the longitudinal direction (Ydirection in the drawing) and are arranged parallel to each other in thelateral direction (X direction) are referred to as X electrodes 1. Theelectrodes which extend in the lateral direction (X direction) so as tointersect with the X electrodes 1 and are arranged parallel to eachother in the longitudinal direction (Y direction) are referred to as Yelectrodes 2.

The touch panel 400 detects changes of electrostatic capacitances of theX electrodes 1 and the Y electrodes 2, and calculates a position wherethe touch panel 400 is touched. A region surrounded by a dotted line 3where the changes of electrostatic capacitances of the X electrodes 1and the Y electrodes 2 can be detected is referred to as an inputregion.

The respective X electrodes 1 and the respective Y electrodes 2 areformed as follows. Both of a width of each X electrode 1 and a width ofeach Y electrode 2 are made small at the intersecting portion 1 a andthe intersecting portion 2 a where the X electrode 1 and the Y electrode2 intersect with each other. Both of the width of the X electrode 1 andthe width of the Y electrode 2 are made large at each electrode portion1 b which is sandwiched between two intersecting portions 1 a and ateach electrode portion 2 b which is sandwiched between two intersectingportions 2 a. Each electrode portion 1 b sandwiched between theintersecting portions 1 a is also referred to as an individualelectrode, and each electrode portion 2 b sandwiched between theintersecting portions 2 a is also referred to as an individualelectrode.

As shown in FIG. 3, a width of the individual electrode 1 b of the Xelectrode 1 in the touch panel 400 is decreased. That is, correspondingto a ratio between the number of the individual electrodes 1 b of the Xelectrode 1 and the number of the individual electrodes 2 b of the Yelectrode 2, an area of the X electrode 1 is decreased so as to beseparated into the individual electrode 1 b and an electrode having afloating potential (dummy electrodes) 4.

Due to such a constitution, an area of the X electrode 1 which isincreased in accordance with the longitudinally elongated shape of thetouch panel 400 can be decreased so that the capacitance of the Xelectrodes 1 on one line becomes substantially equal to the capacitanceof the Y electrodes 2 on one line. Accordingly, noises generated fromthe liquid crystal display panel 600 due to a change of a signal voltagebecome substantially equal between the X electrodes 1 and the Yelectrodes 2.

As described previously, the liquid crystal display panel 600 isprovided with the transparent conductive layer 603 which suppressesinfluences of noises from the liquid crystal display panel 600. However,it is difficult to form the transparent conductive layer 603 on theliquid crystal panel 600 at a high temperature and hence, there may be acase where the transparent conductive layer 603 having sufficiently lowresistance cannot be formed on the liquid crystal display panel 600.Further, even when the transparent conductive layer 603 is formed, theremay be a case where the influence of noises from the liquid crystaldisplay panel 600 causes a problem more or less.

In the related art, although the individual electrode on each one linein the X direction and the individual electrode on each one line in theY direction have the substantially same size, a length of the electrodeon one line in the X direction and a length of the electrode on one linein the Y direction differ from each other and hence, the number ofindividual electrodes differs between the electrodes on one line in theX direction and the electrodes on one line in the Y direction. Hence,the capacitance on one line in the X direction and the capacitance onone line in the Y direction differ from each other. Come to think of atouch panel having a longitudinally elongated shape as an example, thecapacitance of X electrodes corresponding to one line which are arrangedparallel to each other in the Y direction becomes larger than thecapacitance of Y electrodes corresponding to one line which are arrangedparallel to each other in the X direction.

Accordingly, in the touch panel of the related art where the capacitanceof the electrode on one line differs between the X direction and the Ydirection, noise intensity differs between the X direction and the Ydirection. That is, in the touch panel of the related art, the S/N ratiodiffers between the X direction and the Y direction. Due to suchdifference in the S/N ratio, there exists a drawback that the detectionsensitivity of the touch panel as a whole is defined by a lower S/Nratio.

This embodiment can overcome the above-mentioned drawback and canprovide an input device which exhibits a large S/N ratio thus exhibitinggood detection sensitivity. That is, by decreasing an area of theindividual electrode 1 b by division and by forming the floatingelectrode 4, capacitance to ground can be decreased thus lowering anoise level.

In the electrodes shown in FIG. 3, when the floating electrode 4 is notarranged at the individual electrode 1 b, a space portion 8 between theX electrode 1 and the Y electrode 2 which are arranged adjacent to eachother becomes large. Although the X electrode 1 and the Y electrode 2are formed of the transparent conductive film as described previously,an insulation film and the glass substrate are formed in the spaceportion 8 thus forming a region where there is no transparent conductivefilm. A portion where the transparent conductive film is provided and aportion where the transparent conductive film is not provided differfrom each other with respect to transmissivity, reflectance andchromaticity of reflection light and hence, the space portion 8 can beobserved by a user with naked eyes thus lowering quality of a displayimage.

According to our studies, a space appears dimly when a width of thespace portion 8 is 30 μm, and the space substantially completelydisappears when the width of the space portion 8 is 20 μm. Further, whenthe width of the space portion 8 is 10 μm, the space completelydisappears. The narrower the space portion 8, the more capacitancebetween the X electrode 1 and the Y electrode 2 arranged adjacent toeach other by way of the floating electrode 4 becomes. Further,narrowing of the space portion 8 increases the number of defects inwhich the floating electrode 4 is short-circuited with the X electrode 1or the Y electrode 2 due to abnormality in pattern forming attributed toadhesion of a foreign material or the like in steps.

When the individual electrode 1 b of the X electrode 1 and the floatingelectrode 4 arranged adjacent to the individual electrode 1 b areshort-circuited, capacitance to ground of the corresponding X electrodesfor one line is increased so that noises are increased thus giving riseto a drawback that detection sensitivity is lowered. To decrease thecapacitance which is increased when such short-circuiting occurs, thefloating electrode 4 is divided in four as shown in FIG. 3. Although thepossibility of occurrence of short-circuiting failure is lowered whenthe floating electrode 4 is further divided, the number of regions wherethere is no transparent conductive film is increased in the regioncorresponding to the floating electrode 4 and hence, there exists apossibility that the difference in transmissivity, reflectance andchromaticity occurs and is increased between one electrode and theneighboring electrode. Accordingly, as described above, the floatingelectrode 4 is divided in four such that the space between theelectrodes assumes a value narrower than 30 μm, and more preferablyapproximately 20 μm.

In this embodiment, the explanation has been made with respect to thecase in which the touch panel is used in an overlapping manner with thelongitudinally-elongated liquid crystal display device. However, evenwhen the touch panel is used in an overlapping manner with alaterally-elongated liquid crystal display device or an image displaydevice of other type, the present invention can acquire the sameadvantageous effects. Further, the number of division of the floatingelectrode is not limited to four.

Next, FIG. 4 shows the structure in which a flexible printed circuitboard 71 is adhered to a touch panel 400. The flexible printed circuitboard 71 is electrically connected to connection terminals 7 of thetouch panel 400, and supplies various signals outputted from a controlcircuit (not shown in the drawing) to the touch panels 400.

First of all, signals outputted from the control circuit are transmittedto lines 73 which are formed on the flexible printed circuit board 71via external-device-side input/output terminals 74. Through holes 78 areformed in the lines 73 so as to allow the lines 73 to be connected tointersecting lines 77 which are formed on a back surface of the flexibleprinted circuit board 71.

The intersecting lines 77 intersect with a large number of lines 73, andare again connected with the lines 73 via the through holes 78 formed inanother ends thereof. The intersecting lines 77 and the lines 73orthogonally intersect with each other such that an overlapping areabecomes as small as possible. That is, the intersecting lines 77 areformed along the X direction, and the lines 73 are formed along the Ydirection at the intersecting portions. Further, intersecting lines 77are formed not to intersect with power source lines 73-3 having a groundpotential. The lines 73-3 are provided for a shielding purpose. That is,a ground potential (GND) is supplied to the lines 73-3, and the lines73-3 surround other lines 73.

Signals are supplied to the X electrodes 1 and the Y electrodes 2 formedon the touch panel 400 from both ends thus enhancing detection accuracyof the signals. That is, when charges are supplied to each X electrode 1and each Y electrode 2 and amount of times that these electrodes 1, 2respectively acquire fixed voltages are measured so as to detectcapacitance changes, by supplying the charge to each electrode from bothsides, it is possible to suppress errors in measurement attributed toline resistances.

Accordingly, as in the case of Y electrodes 2-1, 2-2 shown in FIG. 4, aline 6-1 is connected to the Y electrode 2-1 from a right side in thedrawing, and a line 6-2 is connected to the Y electrode 2-2 from a leftside in the drawing. In the same manner, the X electrode 1 also has bothupper and lower ends thereof connected to peripheral lines 6.

To supply signals to the X electrodes 1 and the Y electrodes 2 from bothends in this manner, it is necessary to branch a signal outputted fromthe control circuit so as to supply signals to two end portions. In theflexible printed circuit board 71, by supplying the signal outputtedfrom the control circuit to the lines 73-1, 73-2 in a branching manner,it is possible to supply signals to the X electrode 1 and the Yelectrode 2 from both ends.

Further, since the branched lines intersect with other lines, theintersecting lines 77 are formed on the back surface of the flexibleprinted circuit board 71, and the intersecting lines 77 are connected tothe lines 73 via the through holes 78. That is, the through holes 78play a role of connecting the lines 73 to the intersecting lines 77arranged on the back surface of the flexible printed circuit board 71and a role of branching the signals. Since the signals are branched onthe flexible printed circuit board 71, the number of lines through whichsignals are supplied on a touch panel 400 side is increased compared tothe number of lines through which signals are supplied on anexternal-device-side input/output terminal 74 side.

The supply of signals to the X electrodes 1 and the Y electrodes 2 fromboth ends generates a particular drawback that the lines intersect witheach other. Particularly, when the connection terminals 7 are formed ona short side of the touch panel 400, the X electrodes 1 which extend inthe longitudinal direction (in the Y direction in the drawing) and arearranged parallel to each other in the lateral direction (in the Xdirection) are connected to lines 6-b of the peripheral lines 6 arrangedin the vicinity of the center of the touch panel 400 and lines 6-a ofthe peripheral lines 6 arranged in the vicinity of outer edges of thetouch panel 400.

Accordingly, on the flexible printed circuit board 71, the intersectinglines 77 which connect the lines 6-b and the lines 6-a intersect withmany other lines 73. Accordingly, the line capacitance of the Xelectrode 1 becomes larger than the line capacitance of the Y electrode2. As mentioned previously, the X electrodes 1 also have the drawbackthat the area of the X electrode 1 is increased in accordance with thelongitudinally elongated shape of the touch panel 400 and hence, the Xelectrodes 1 are liable to be more easily influenced by noises than theY electrodes 2. Accordingly, when the connection terminals 7 are formedon the short side of the touch panel 400, it is effective to adopt theconstitution in which the area of the X electrode 1 is decreased so asto set the capacitance of X electrodes 1 on one line substantially equalto the capacitance of the Y electrodes 2 on one line thus making anamount of noises generated by fluctuation of a signal voltage generatedfrom the liquid crystal display panel 600 substantially equal betweenthe X electrodes 1 and the Y electrodes 2.

Next, FIG. 5 shows the constitution of a liquid crystal display devicehaving a touch panel 400 which can easily mount a spacer 30. That is,the spacer 30 is adhered to a flexible printed circuit board 71, and atouch panel 400 and the spacer 30 are integrally formed with each other.Thereafter, the touch panel 400 is assembled to the liquid crystaldisplay panel 600.

The spacer 30 is adhered, using an adhesive agent or the like, to theflexible printed circuit board 71 adhered to the touch panel 400 thusfacilitating mounting of the spacer 30 on the liquid crystal displaypanel 600. Further, by adhering the spacer 30 to the flexible printedcircuit board 71, the flexible printed circuit board 71 can absorb aminute step.

Further, in FIG. 5, a polarizer 601 is arranged between the touch panel400 and a front window 12. By arranging the polarizer 601 on the touchpanel 400, it is possible to decrease the frequency of occurrence of adrawback that an electrode pattern of the touch panel 400 is observed.

Next, a manufacturing method of the touch panel according to the presentinvention is explained in conjunction with FIG. 6A to FIG. 9B. FIG. 6A,FIG. 7A, FIG. 8A and FIG. 9A are respectively schematic cross-sectionalviews taken along a line B-B′ in FIG. 3 showing respective steps of themanufacturing method. In the same manner, FIG. 6B, FIG. 7B, FIG. 8B andFIG. 9B are respectively schematic cross-sectional views taken along aline C-C′ in FIG. 3 showing respective steps of the manufacturingmethod.

First of all, a first step is explained in conjunction with FIG. 6A andFIG. 6B. In the step shown in FIG. 6A and FIG. 6B, a first ITO film 14(Indium Tin Oxide) having a film thickness of approximately 15 nm isformed on a glass substrate 5 and, thereafter, a silver alloy filmhaving a film thickness of approximately 200 nm is formed on the ITOfilm 14. A resist pattern is formed in a photolithography step, and thesilver alloy film is patterned. Next, the resist is peeled off andremoved, a resist pattern is formed in a photolithography step, and thefirst ITO film 14 is patterned. Then, the resist is peeled off andremoved thus forming the patterned ITO film 14 and the silver alloy film15 as shown in FIG. 6A and FIG. 6B. Since the silver alloy film 15 isnon-transparent, to avoid the observation of the silver alloy film 15,the silver alloy film 15 is removed from a portion where the silveralloy film 15 covers a display region of the liquid crystal displaypanel 600 which is overlapped to the glass substrate 5 later so that thesilver alloy film 15 is formed only on the peripheral lines 6.

Next, the second step is explained in conjunction with FIG. 7A and FIG.7B. To the glass substrate 5 on which the first ITO film 14 and thesilver alloy film 15 are patterned, a photosensitive interlayerinsulation film 16 is applied by coating, and the interlayer insulationfilm 16 is patterned using a photolithography technique. It is desirablethat the interlayer insulation film 16 is a film containing SiO2 as amain component and having a film thickness of 1 m or more. As shown inFIG. 7B, contact holes 17 are formed in a peripheral portion of theinterlayer insulation film 16. Further, the interlayer insulation film16 is removed at a connection terminal portion which is provided forconnection with an external drive circuit.

Next, the third step is explained in conjunction with FIG. 8A and FIG.8B. A second ITO film 18 having a film thickness of approximately 30 nmis formed, a resist pattern is formed by photolithography, and thesecond ITO film 18 is patterned. Then, the resist is peeled off andremoved thus forming the second ITO film 18 as shown in FIG. 8A and FIG.8B.

Next, the fourth step is explained in conjunction with FIG. 9A and FIG.9B. A film equal to the insulation film used in the second step isapplied to the glass substrate again as an uppermost protective film 19.The uppermost protective film 19 is patterned by photolithography. Thetouch panel 400 is formed through the above-mentioned steps.

As has been explained above, according to the present invention, in theelectrostatic capacitive type sensor for the display device whichdisplays image information or character information, it is possible tomanufacture a touch panel which exhibits excellent detectionsensitivity. According to the present invention, the input detectionregion is not limited to any particular shape, and the shape of theindividual electrode is also not limited to any particular shape.Further, in the above-mentioned embodiment, the explanation is made withrespect to electrodes extending in the X direction and the electrodesextending in the Y direction which orthogonally intersect with eachother. However, so long as these electrodes are provided for enhancingan S/N ratio between electrode lines for detecting an input position,the present invention is also effectively applicable to capacitancesbetween electrodes which intersect with each other obliquely orcapacitances between electrodes which differ from each other in lengthand extend parallel to each other.

Although the invention made by inventors of the present invention hasbeen specifically explained in conjunction with the embodimentheretofore, it is needless to say that the present invention is notlimited to the above-mentioned embodiment and various modifications areconceivable without departing from the gist of the present invention.

What is claimed is:
 1. A touch panel comprising: a substrate including aplurality of X electrodes formed along a X direction and a plurality ofY electrodes formed along a Y direction, and a flexible printed circuitboard connecting the touch panel, the flexible printed circuit boardhaving a first signal line supplying a signal to the plurality of Xelectrodes and a second signal line supplying a signal to the pluralityof Y electrodes wherein the flexible printed circuit board has a firstconductive layer and a second conductive layer, a first portion of thefirst signal line is made of the first conductive layer, a secondportion of the second signal line is made of the second conductive layerand intersects the first portion of the first signal line, the touchpanel has a floating electrode which is made of the conductive layer ofthe plurality of X electrodes and the plurality of Y electrodes, anddoes not connect the plurality of X electrodes and the plurality of Yelectrodes, the plurality of X electrodes has a first edge which doesnot extend along the X direction, the plurality of Y electrodes has asecond edge which does not extend along the Y direction, the floatingelectrode has a third edge which extends along the first edge and afourth edge which extends along the second edge, and the floatingelectrode does not overlap the X electrode and the Y electrode, and doesnot electrically connect with the first and second signal line.
 2. Thetouch panel according to claim 1, wherein the floating electrode doesnot overlap with the plurality of X electrodes and the plurality of Yelectrodes.
 3. The touch panel according to claim 1, wherein either oneof the plurality of X electrodes and the plurality of Y electrodes ismade of a transparent conductive film.
 4. The touch panel according toclaim 1, wherein the plurality of X electrode and the plurality of Yelectrode are formed with an insulation film sandwiched therebetween. 5.The touch panel according to claim 1, wherein the touch panel has aplurality of first connection terminals which is made of a metalmaterial.
 6. A touch panel comprising: a substrate including a pluralityof X electrodes formed along a pair of long sides of the touch panel anda plurality of Y electrodes formed along a pair of short sides of thetouch panel, and a flexible printed circuit board connecting the touchpanel, the flexible printed circuit board having a plurality of firstsignal lines electrically connecting the plurality of X electrodes and aplurality of second signal lines electrically connecting the pluralityof Y electrodes wherein the flexible printed circuit board has a firstconductive layer and a second conductive layer, a first portion of theplurality of first signal lines is made of the first conductive layer, asecond portion of the plurality of second signal lines is made of thesecond conductive layer and intersects the first portion of theplurality of first signal lines, the touch panel has a floatingelectrode which is between one of the plurality of X electrodes and oneof the plurality of Y electrodes, and does not connect the plurality ofX electrodes and the plurality of Y electrodes, the floating electrodehas an edge which does not extend along the pair of long sides and thepair of short edges, and the floating electrode does not overlap the Xelectrode and the Y electrode, and does not electrically connect withthe first and second signal line.
 7. The touch panel according to claim6, wherein the floating electrode is formed adjacent the plurality of Xelectrodes.
 8. The touch panel according to claim 6, wherein either oneof the plurality of X electrodes and the plurality of Y electrodes isformed of a transparent conductive film.
 9. The touch panel according toclaim 6, wherein the plurality of X electrodes and the plurality Yelectrodes are transparent conductive films which are formed with aninsulation film sandwiched therebetween.
 10. The touch panel accordingto claim 6, wherein the floating electrode is made of a transparentconductive film.
 11. A touch panel comprising: a substrate including aplurality of X electrodes formed along a pair of long sides of the touchpanel and a plurality of Y electrodes formed along a pair of short sidesof the touch panel, and a flexible printed circuit board connecting thetouch panel, the flexible printed circuit board having a plurality offirst signal lines supplying a signal to the plurality of X electrodesand a plurality of second signal lines supplying a signal to theplurality of Y electrodes wherein the flexible printed circuit board hasa first conductive layer and a second conductive layer, a first portionof the plurality of first signal lines is made of the first conductivelayer, a second portion of the plurality of second signal lines is madeof the second conductive layer and intersects the first portion of theplurality of first signal lines, the touch panel has a plurality offloating electrodes which is formed adjacent the plurality of Xelectrodes respectively and does not contact the plurality of Xelectrodes, the plurality of floating electrodes has an edgerespectively which does not extend along the pair of long sides and thepair of short edges, and the floating electrode does not overlap the Xelectrode and the Y electrode, and does not electrically connect withthe first and second signal line.
 12. The touch panel according to claim11, wherein the floating electrode does not overlap with the pluralityof X electrodes and the plurality of Y electrodes.
 13. The touch panelaccording to claim 11, wherein either one of the plurality of Xelectrode and the plurality of Y electrodes is made of a transparentconductive film.
 14. The touch panel according to claim 11, wherein theplurality of X electrodes and the plurality of Y electrodes are formedwith an insulation film sandwiched therebetween.
 15. The touch panelaccording to claim 11, wherein the floating electrode is made of atransparent conductive film.